This application claims the priority of German patent application 198 09 516.3, filed Mar. 5, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method and apparatus for automatically changing rolls of self adhesive protective film.
In the mass production of motor vehicles, the vehicles must be prepared for shipment so that they do not suffer any damage, especially so that paint is not adversely affected by shipment and weathering influences. If shipment by rail or ship is required for transport to the customer, it has been conventional heretofore to coat vehicles with a protective layer of wax which must be removed before delivery to the customer. Removing the protective wax without leaving any residue was not only a labor-intensive task but also imposed burdens on both people and the environment because of the solvents used. Therefore, a change has recently been made to protecting bodies during shipment by using self-adhesive films.
Such films are usually pulled manually from a film roll and applied to the parts to be protected. It is also known to mount film rolls in a holder and to pull the film off under machine control. Replacement of such film rolls has proven to be very labor-intensive. For example, the remaining film supply must be constantly monitored so that the film roll can be replaced when its end is reached. The used film roll must then be removed and replaced by a new film roll. Since the new film roll is usually not stored in the immediate vicinity of a film application device, this results either in prolonged production interruptions or a need for an operator constantly to monitor the film roll as it unrolls so that preparation for replacement can begin shortly before the end of the film roll.
Hence, one object of the invention is to provide a method and apparatus for automatically changing film rolls, in which the replacement of film rolls is less awkward by comparison with the prior art, so that production interruptions can be avoided. Another object of the invention is to eliminate the need for extra personnel to monitor the production process with regard to the changing of film rolls.
Still another object of the invention is to provide a method and apparatus by which, all of the film roll changers can be loaded at any desired point in time in order thus to ensure that the film length is sufficient for an entire shift for example.
These and other objects and advantages are achieved by the method and apparatus according to the invention, in which simple automatic changing of film rolls is possible without production interruptions, by moving a replacement roll (second film roll), which is stored in a standby position in the device, into a working position, in which film can be pulled from a film roll (first film roll). By a suitable choice of film roll sizes it is possible to perform an adjustment to a film length that is required for example during a shift.
Since it was conventionally possible to provide a replacement roll only immediately when a film roll ran out or reached the end or to load it into the changing device, the device according to the invention represents a considerable simplification. An operator can, within certain time limits, load the device according to the invention with another film roll at any time without adversely affecting the production process in any way. The loading process can be performed during a shift or between two shifts for example or during the unsticking process. Furthermore, the film roll can be changed in a very simple fashion essentially by means of a single traveling movement of a replacement roll, since a used film roll can be removed from the working position by moving the replacement roll and then bringing the replacement roll into the working position.
According to one preferred embodiment of the invention, the device has an ejection device with means for holding or moving the second film roll, by means of which the first film roll can be removed from the working position during the movement of the second film roll. This makes it possible to change a film roll in an especially simple and mechanically reliable fashion.
Advantageously, the device according to the invention has a lifting device for essentially vertical movement of a pallet on which the second film roll can be placed, especially on rotatable support rollers. By means of such a lifting device, the second film roll can be brought into the working position in a simple fashion. Furthermore, the rotatable support rollers facilitate pulling off the end of the film for sticking it to a locking tube, described below.
Advantageously, the device has a pivotable ejection loop that is connected with the pallet for removing the first film roll from the working position as the second film roll moves vertically. Such an ejection loop can remove a film roll to be replaced from its holder in simple fashion during the upward lifting movement of the pallet, and the loop can be guided past a new film roll held in the working position during a subsequent downward movement because of its ability to pivot.
According to one preferred embodiment, the pallet can be positioned on a carriage which can be introduced into a frame of the device in such fashion that the second film roll located on the pallet can be brought into the standby position. A carriage of this type makes it possible in simple fashion to introduce a new film roll into the device at any point in time during the operation of the device, such as during the pulling of the film from the first film roll, without adversely affecting operation in any way whatever. The carriage can have a plurality of rollers that can be made rotatable depending on the space conditions. As a result, movement of the carriage between a film roll storage area and the device for changing film rolls can be accomplished in simple fashion.
Advantageously, at least two centering pins are provided to secure the pallet in position on the carriage. With such centering pins, the pallet can be suitably positioned on the carriage that can be introduced into the device.
According to one preferred embodiment, the device has a compensating roller that is drivable and/or brakable and can be brought into an operating connection with the first film roll. By means of such a compensating roller, when the film is pulled off the film roll, its pulling edge can be secured in simple fashion, with the pulling off of the film being supported if necessary by a corresponding rotary movement of the compensating roller. Furthermore, the roll can advantageously also be drivable in the opposite direction so that film that has been pulled off can be rewound by means of the compensating roller. The ability to brake the film roll ensures a defined pulling off of the film.
Advantageously, the device also has a measuring means that can be brought into an operating connection with the first film roll, especially a measuring wheel for measuring the film pulled off the film roll, and with signal generating means cooperating with the measuring means to output a signal to a control device on the means for triggering the lifting or movement of the second film roll. As a result, in simple fashion, it is possible to determine the length of the film pulled off the film roll that is in the working position. When the end of the film is reached, it is then possible to replace the old film roll by a new film roll. The measuring wheel can generate a signal suitable for this purpose and send it to control means or transmit it directly to the lifting device.
According to one preferred embodiment, a locking tube is mounted on the lifting device or the pallet, to which tube the beginning of the film pulled off the second roll can be secured. As a result, the end of the film that has been pulled off the second film roll can be secured in simple fashion so that after the second film roll moves into the working position, further pulling off of the film is simplified.
Advantageously, the device according to the invention has a suction strip by means of which the film end of the second film roll secured to the fixing tube, when the working position is reached, can be secured further in preparation for pulling off the film as provided.
Advantageously, a cutting device is provided for cutting the film between the locking tube and the suction strip. As a result, the end of the film on the second film roll can be separated in simple fashion from the locking tube so that the tube, together with the pallet or the lifting device, can be lowered again.
According to one preferred embodiment of the method according to the invention, when the signal indicating the end of the film on the first film roll is generated, before or during the lifting or movement of the second film roll, the film that has already been pulled off the first film roll and not yet cut is rewound on the film roll. As a result, the first film roll can be removed subsequently from the working position in a very simple fashion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.